[PATCH QEMU HCI-8.1 v2 04/24] vfio/pci: Fix information leak in vfio_rom_read()

[Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>]

From: Cédric Le Goater <clg@redhat.com>

vfio_rom_read() can leak uninitialized stack data to the guest when a
read occurs at the end boundary of the ROM BAR.

Fix this by initializing the val union to 0xff, matching the ROM
initialization pattern used in vfio_pci_load_rom().

andrey.drobyshev:
    This commit is cherry-picked as-is, with no modifications, from the
    upstream commit 402fd5a75659.

Reviewed-by: Philippe Mathieu-Daudé <philmd@mailo.com>
Reviewed-by: Mario Casquero <mcasquer@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20260602074446.1206892-1-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
 hw/vfio/pci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index d930ef46309..fa2ca0d779d 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -1153,7 +1153,7 @@ static uint64_t vfio_rom_read(void *opaque, hwaddr addr, unsigned size)
         uint16_t word;
         uint32_t dword;
         uint64_t qword;
-    } val;
+    } val = { .qword = ~0ULL };
     uint64_t data = 0;
 
     /* Load the ROM lazily when the guest tries to read it */

-- 
2.47.1